Railway traffic controlling apparatus



April 6, 1943; WALLACE 2,315,886

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 17, 1941 7 Sheets-Sheet l 339K199 QQQI 00100 C i 007 E10 11! E100 i 211 20 3 INVENTOR HIS ATTORNEY April 1943- H. A. WALLACE 2,315,886

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 17, 1941 7 Sheets-Sheet 2 1 QB I Z6 97 (5 A INVENTOR Herb Awallace Fig 11 HIS ATQTORNEY April 6,1943. WALLACE 2,315,886

RAILWAY TRAF FIC CONTROLLING APPARATUS Filed Sept. 17, 1941 7 Sheets-Sheet '4 a .5 7; )5 s -a 6 E 9, 713T cg -/6RT 86?? 0 10 E 8612 107 109 45 INVENTOR Herb Awallace HIS AfiOkNEY P 1943- H. A. WALLACE 2,315,886

RAILWAY TRAFFIC CONTROLLING APPARATUS 7 Sheets-Sheet 5 Filed Sept. 17, 1941 INVENTOR v I Herb z Awallace 1e BY g4 g.

H16 AT'ITORAIEY April 6, 1943. H. A. WALLACE 2,315,336

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 1'7, 1941 '7 Sheets-Sheet 6 April 6, 1943. H. A. WALLACE 2,315,386

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 1'1, 1941 7 Sheets-Sheet 7 8 I INVENTOR Her 1 A.Wallace m6 Ai'TORNEY Patented Apr. 6, 1943 RAHJWAY TRAFFIC CONTROLLING APPARATUS Herbert A. Wallace, Edgewood, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa, a corporation of Pennsylvania Application September 17, 1941, Serial No. 411,160

8 Claims.

My invention relates to railway traffic controlling apparatus, and it has particular reference to the organization of such apparatus into railway signal systems of the class employing coded track circuits for controlling either or both wayside signals and train-carried cab signals. More particularly, my invention relates to absolute permissive block (A. P. B.) and other systems for controlling trafiic in both directions on a stretch of single track railway, wherein the line wires usually required in such systems are obviated by providing in each track section two track circuits, one for each direction of traffic, arranged to be independent of each other and having their energizations independently coded in accordance With traflic conditions in advance.

An object of my invention is to provide novel and improved absolute permissive block signal systems involving coded track circuits arranged to obviate control line wires.

Another object of my invention is to provide systems of the above-mentioned class arranged to control either or both wayside signals and train-carried cab signals.

A further object is to provide systems of the above-mentioned class involving apparatus arranged to effect the control of train-carried apparatus responsive to track circuit current having certain distinctive characteristics.

An additional object is to provide systems of the above-mentioned class arranged so as to utilize track circuit current having certain distinctive characteristics for the control of traincarried apparatus irrespective of the direction of train movement over the stretch.

The above-mentioned and other important objects and characteristic features of my invention which will become readily apparent from the following description, are attained in accordance with my invention by employing two different frequencies of alternating current one having the frequency commonly used in railway signaling for controlling train-carried apparatus such as cab signals or train control apparatus, and the other having a frequency distinctively different from the one frequency. Each section is provided with two track circuits one supplied at one end of the section with current of the one frequency for transmission through the rails to the other end, and the other track circuit supplied at the other end with current of the other frequency for transmission to the one end of the section. The apparatus further is arranged to control the frequency of current supplied to the circuits of each section so as to supply current of the one or train control frequency always toward a train on the stretch irrespective of the direction of its movement over the track.

Other objects and advantages of my invention reside in the organization of apparatus into absolute permissive block railway signal systems, as will be made clear in the following description.

I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1a to lg, inclusive, when placed side by side with Fig. 1a on the left, comprise a composite view showing diagrammatically one form of apparatus embodying my invention.

Referring to the drawings, the reference characters I and la designate the track rails of a stretch of railway track X connected with successive passing sidings Y and Z by switches which are designated by the reference characters W with suitably distinguishing sufiixes. Although only one end of siding Y is shown in the drawings, it is to be understood that both ends of this siding are connected with the stretch similarly to siding Z. The rails of the stretch X are divided by insulated joints 2 into a plurality of successive adjoining track sections JK, K-L, etc.

The reference characters S with distinguishing sufiixes designate signals for governing traffic on stretch X. Eastbound traffic, that is, trafiic operating from left to right as viewed in the drawings, is governed between sidings Y and Z by signals 28 and 68, while traffic in the opposite'or westbound direction between the two sidings is governed by signals 9S and 58. Other signals IS and IDS are provided for governing the entrance of traffic into the siding section extending immediately to the west or'to the left of section JK,:md section N-'-O extending to the right of section MN, respectively. In addition, signals I33 and HES are provided at P for governing traflic entering and leaving section OP, respectively. These signals may be of any desired type, but for the purposes of this description it is assumed that the signals are of the searchlight type each having an operating mechanism such as is shown in United States Letters Patent No. 2,172,724 granted on September 12, 1939 to Wesley B. Wells and William K. Lockhart for Light signals. It is deemed sufiicient to state that when the mechanism of a signal S is energized by cu rent of one polarity, it is conditioned to display its clear aspect, when energized by current of the opposite polarity, the signal is conditioned to dis play its approach aspect, and when the mecha nism is deenergized the signal is conditioned to display its stop aspect. Each signal also is provided with an associated circuit controller comprising a movable member 4 which is operated by the associated mechanism into its upper or front position when the signal is conditioned to display either its clear or its approach aspect, and which member is operated by the signal mechanism out of its front and into its back position when the signal is conditioned to display its stop aspect. It is, of course, to be understood that the specific arrangement of signals shown in the drawings is merely illustrative and other arrange ments of signals may be employed. For example, additional signals may be provided for the stretch, in pairs, as at locations corresponding to L, or singly if desired.

The wayside signals S are arranged to be controlled in accordance with the usual A. P. B. principle of signaling by apparatus arranged to provide each track section with two track circuits one for each direction of traffic. One of the track circuits of each section is normally supplied with coded track circuit energy of the type adapted to effect control of the usual traincarried apparatus, while the other of the track circuits of each section may be supplied with coded track circuit energy of a distinctive character. Each track circuit includes a track relay,

designated by the reference character 'I'R, with a suitably distinguishing prefix, and each track relay has associated therewith tuning means hereinafter referred to and controlled in a manner described in detail later whereby each relay TR is conditioned to respond uniquely to the type of current supplied to its associated circuit.

More specifically, each section is supplied at one of its ends with coded alternating track circuit current having the frequency, which I shall refer to as the train control frequency, adapted to effect control of the usual train-carried apparatus. This train-carried apparatus may, for example, be of the type shown in United States Letters Patent No. 1,773,515, granted to C. C. Buchanan on August 19, 1930, and such apparratus is generally tuned to current of a particular frequency (usually 100 cycles per second) distinctively different from the ordinary commercial frequencies, thereby preventing interference with or false operation of the train-carried apparatus due to stray currents of commercial frequencies in the track rails. The other end of each of the sections is normally supplied with coded alternating track circuit current having a frequency distinctively different from the train control frequency and hence ineffective to control the previously mentioned train-carried apparatus. Section J--K, for example, is supplied at its end K with train control current through the medium of a track transformer 3TT having its secondary winding 5 connected to the track rails and having its primary winding 6 connected through a circuit shortly to be traced, to a line transformer LT3 connected across line wires 1 and 8 extending along the trackway. These wires preferably are connected to a suitable source of alternating current, such as a generator not shown but generating alternating current having the previously mentioned train control frequency of 100 cycles per second. The train control energy supplied to section J-K is conducted through the track rails to the other end J of the section to operate the associated track relay 2TB. This relay is supplied with energy derived from the rails through the medium of a relay transformer ZR'I which has its primary winding 9 connected to the rails and has its secondary winding l0 connected through a rectifier H to relay ZTR. The connection of rectifier H to relay transformer ZRT is tuned, as shown, by means of a condenser [E to resonance at the train control frequency. At times, however, this connection may be tuned by means of a condenser It to resonance at the other or second frequency, and condenser [2 or I3 is rendered effective to tune such connection to resonance according as contact I4 of the relay 3TP, hereinafter referred to, is in its normal right-hand position, as viewed in Fig. 1a, or is in its reverse (left-hand) position,

respectively.

Section JK also is supplied at its end J with track circuit current of the second frequency through the medium of a track transformer ZTT having its secondary winding 5 connected to the track rails and having its primary winding 6 connected through a circuit shortly to be traced, to a suitable source of current having the second frequency. Current of the other or second frequency may be derived, for example, from a pair of line wires supplied with current of such other frequency, but as shown section J-K is supplied with current of the second frequency from a secondary winding l5 of a transformer FT forming a part of a frequency changer PC, which frequency changer comprises a rectifier l5 having its input terminals connected through line transformer LTI to the line wires 1 and 8 and.

having its output terminals connected to primary winding I! of transformer FT. It is readily apparent that rectifier 16 when energized by current of the first frequency supplies two pulses of unidirectional current to winding ll of transformer FT in each cycle of alternating current, hence there is induced in secondary winding l5 by these double frequency pulses of unidirectional current, an alternating electromotive force having a frequency which is double the frequency of current in wires 1 and 8. It follows, therefore, that secondary winding [5 of transformer FT may be considered as a source of alternating current having a second frequency of 200 cycles per second, or a frequency distinctively different from the alternating current of the first or train control frequency.

The current of the second frequency supplied to section J-K is conducted through the track rails to the other end K of the section to operate the associated track relay 3TB. This relay is supplied with energy derived from the rails through the medium of a relay transformer 3RT which has its primary winding 9 connected to the rails and has its secondary winding It] connected through a rectifier II to relay 3TB. The connection of rectifier II to relay transformer SRT is tuned, as shown, by means of a condenser l3 to resonance at the second frequency. At times, however, this connection may be tuned by means of condenser I2 to resonance at the first or train control frequency, and condenser i3 or [2 is rendered effective to tune such connection to resonance according as contact 18 of a relay 3SP, hereinafter referred to, is in its normal released position or is in its attracted front position, respectively.

The track circuit currents supplied to each section are coded in the manner usual in coded signal systems. The current of the second frequency supplied at J to section JK, for example, is coded through the medium of a suit able code transmitter or coder ICT, which is represented conventionally in the drawings as comprising a constantly energized winding operating a plurality of contacts I and a at a rate of 75 times per minute and a plurality of contacts I30 and I891: at a rate of 180 times per minute. The current of the first frequency supplied to section J--K at K is coded in a manner to be explained presently.

The track relays TR of each section have associated therewith code responsive apparatus arranged to respond to frequency type code energy. This code responsive apparatus comprises a decoding transformer, designated by'the reference character DT with a suitably distinguishingprefix, a code detecting relay designated by thereference character H with a distinguishingprefix, and certain of the code responsive means include a code selecting relay, designated by the reference character D with a prefix, and a decoding unit DUIBI].

The decoding transformer 3DI included in thecode responsive apparatus associated with relay 8TB of section JK, for example, has one terminal C of a suitable source of unidirectional current, such as a battery not shown but having its opposite terminals designated by the reference characters B and 0, connected to a mid terminal tap of primary winding 2| and has the other ter minal B of the source connected to one end or the other of winding 2I according as contact 22 of relay 3TR, is in its upper or its released position, respectively. As is readily apparent, the direction of flux in transformer winding 2| is reversed at a rate corresponding to the rate at which relay 3TB, operates its contact 22, hence there is induced in the secondary winding 24 of an alternating electrcmotive the transformer force having a frequency corresponding to the code rate of operation of relay 3TB. Relay 3H associated with transformer 3DT is connected over contact 23 of relay 3TB, to secondary winding 24 of the transformer ina manner simliar to that described in detail in United States Lettel's Patent No. 2,237,788, granted on April 8, 1941, to Frank H. Nicholson and Leslie R. Allison. whereby relay SE is supplied with substantially unidirectional current from transformer 3DT. The relay 3H and transformer 3DT are proportioned and constructed in such manner that relay 3H is effectively energized whenever relay STR operates at any of the usual code rates of 75 or more code cycles per minute, but not when relay 3TB operates at a relatively slow code rate of, say, code cycles per minute. Relay 3H accordingly functions as a code detecting relay in that it detects operation of its associated track relay at any of the usual code rates of 7-5 or more code cycles per minute. Relay 3H associated with relay 3TB, has associated therewith a slow releasing relay Sl-IP controlled over an obvious circuit including front contact 25 of relay 31-1.

The code responsive apparatus associated with relay ZTR of section JK includes. in addition to decoding transformer ZDT and relay 2H ar ranged in a manner corresponding to that just mentioned, a. code selecting relay 2D connected through a decoding unit DUISil to transformer ZDT. The details of construction of decoding unit DUIS!) are not shown in the drawings, but such a unit usually comprises a reactor condenser tuning unit tuned to resonance at a frequency corresponding to the 180 code rate, whereby relay 2D is effectively energized when and only when the associated relay 2TB operates at the ation of its associated track relay at the code rate.

The code responsive apparatus associated with relay iTR of the section immediately to the left,

as viewed in Fig. 1a of the drawings, of section J-K includes, in addition to decoding transformer IDT, code detecting relay IH and repeater iHP, and code selecting relay ID, another or slow code detecting relay BSA and a relay FSA. Relay FSA is arranged with its winding interposed in the circuit connection of front contact 22 of relay iTR to a portion of primary winding 2! of transformer ID'I', and relay FSA when energized closes its front contact 28 to complete an obvious circuit including relay BSA and over which another portion of winding H of transformer IDT is energized when back contact 22 of relay ITR, is closed. The relays FSA and BSA are preferably sufficiently slow releasing to bridge respectively the off and on intervals of 20 code energy, hence when relay I TR operates in response to energy coded at the rate of 20 or more cycles per minute, relay FSA is energized each time relay ITR closes its front contact 22 in response to an on interval of code energy received from the rails of the section, and with front contact 26 of relay FSA closed, relay BSA is energized each time relay ITR, closes its back contact 22 in response to an off interval of code in the associated section. When, however, relay ITR, is steadily energized, relay BSA is releasedsince its energizing circuit is then held open at back contact 22 of relay ITR, or if relay ITR, is steadily released, both relays FSA and BSA are released since relay FSA is deenergized when its energizing circuit is held open at front contact 22 of relay iTR and with contact 26 of relay FSA open, relay BSA is likewise deenergized. It follows, therefore. that relay BSA is energized when and only when its associated track relay ITR operates in response to coded energy received from its associated section, and by properly proportioning the release periods of relays FSA and BSA, relay BSA may be employed to detect operation of its associated track relay HR in response to energy coded at the rate of 29 or more cycles per minute.

, Each signal S is controlled by the decoding a1oparatus associated with the track relay TR having its prefix corresponding .to the prefix em-- ployed in the reference character of the signal. For example, signal IS is controlled by the code responsive apparatus associated with relay ITR, this control being effective when relays IH and ID, associated with relay ITR, are picked up, to energize the mechanism of signal I S by cur-.

rent of normal polarity so that signal I S is caused to display its clear aspect; when relay 5D is released but relay IH is picked up, the polarity of energy supplied to the mechanism of signal IS is reversed and the signal is caused to display its approach aspect; and when both relays IH and ID are released, the mechanism of signal IS is deenergized and signal iS is caused to display its stop aspect.

The reference characters SR with suitably dis- I tinguishing sufiixes designate stick relays arcircuits and function of the stick relays will be pointed out as the description proceeds. Certain of the stick relays are provided with slow releasing repeater relays, designated by the reference character SP with suitably distinguishing prefixes.

The apparatus embodying my invention further includes relays 3'I'P, 8'1? and I5TP arranged in a manner explained presently to establish overlap control.

In order to simplify the drawings, I have represented contacts of relays at times disposed remote from the relays operating such contacts, but in each case each of such contacts has been represented in the normal condition which it assumes and has been identified not only by a reference character individual to such contacts, but also by placing immediately above such contact the reference character of the relay causing that contact to operate. For example, the reference character 3SP has been placed immediately above back contact I8 to indicate that this contact is operated by relay 38?, and the contact is represented in a closed position to indicate that such relay is normally deenergized.

As represented in the drawings, the apparatus embodying my invention is in its normal condition, that is, each section represented in the drawings is unoccupied, each section (not shown) between section JK and the next siding to the west of siding Y is unoccupied and each section (not shown) between section OP and the next siding east of siding Z is unoccupied. With these various sections mentioned unoccupied, the track circuits of the sections represented in the drawings are supplied with track circuit current coded at the 180 code rate, the track relays TR shown in the drawings are caused to operate at the normal or 180 code rate, the associated code responsive relays D and H are picked up, the signals S are caused to display their respective clear aspects, and the stick relays SR are released.

In this normal condition of the apparatus, relay ITR associated with the section to the left of section JK is tuned to respond to current of the train control (100 cycle) frequency and is caused to operate at the 180 code rate in response to energy supplied to the rails of the associated section in a manner corresponding to that hereinafter pointed out whereby the rails of section O-P are supplied at O with track circuit energy. Relays ID, IH, IHP, FSA and BSA associated with relay l'IR accordingly are energized, signal IS is energized by current of normal polarity and is caused to display its clear aspect, and relay ISR is released. With relay ISR released and signal IS in its clear position, current of the second (200 cycle) frequency coded at the 180 code rate is supplied to section JK at J over a circuit extending from one terminal of winding I5 of frequency changer FC through contact 21 of relay 3TP in its normal position, contact I80 of coder ICT, contact 4, operated by signal IS, in its front position, and secondary winding 6 of track transformer 2TT through a common connection, indicated by the reference character CC, to the other terminal of winding I5. It is to be noted that if contact 21 of relay 3TP is in its reverse or left-hand position and all other parts of the just traced circuit are unchanged, then the secondary winding of line transformer LTI would be connected to the circuit and current of the first (train control) frequency coded at the 180 code rate would then be supplied at J to section JK. Likewise, it

is to be noted that if contact 4 of signal IS is operated from its front to its back position (as when signal IS is caused to display its stop aspect), then the current supplied at J to section JK would be carried through contact I5 of coder ICT and accordingly would be coded at the '75 code rate.

The track circuit current coded at the 180 code rate normally supplied at J to section JK causes operation of relay 3TB which is tuned by condenser I3 to be responsive to current of the second (200 cycle) frequency. Relays 3H and 3HP associated therewith are energized, and current of the second frequency is supplied at K to section KL over a circuit extending from one terminal of winding I5 of frequency changer FC through back contact 28 of relay 3SR, front contact 33 (when closed) of relay 3TR, and primary winding Ii of track transformer 4TT through common connection CC to the other terminal of winding I5. It is to be noted that if contact 28 of relay SSR is operated to its front position, the current supplied over the just traced circuit is then shifted from the second to the first frequency.

The track circuit current normally supplied at K to section KL is caused to be coded at the 180 code rate in response to relay 3TB following 180 code energy received from its associated section JK, and this current in section K-L causes relay 5TB. to respond since it is tuned by condenser I3 to respond to current of the second frequency. Relays 5D, 5H and 5HP associated with relay 5TB accordingly are energized, and signal SS is caused to display its normal clear aspect.

Section L-M is supplied at L with current of the first (100 cycle) frequency over a circuit which may be traced from one terminal of the secondary winding of line transformer LT5 through back contact 29 of relay BSR, contact I of coder 2CT, contact 4, operated by signal SS, in its front position, and primary winding 6 of track transformer fiTT through common connection CC to the other terminal of the secondary winding of transformer LTB. This current is coded at the 180 code rate and causes relay 'ITR, tuned by condenser I2 to respond to current of the first frequency, to operate at the 180 code rate and cause its associated relays 1H and 'IHP to be picked up. The operation of relay 'ITR at the 180 code rate causes the coding at this rate of the current of the first frequency supplied at M to section M-N over a oil'- cuit extending from one terminal of line transformer LTl through back contact 31 of relay 8SR, front contact 30 when closed of relay ITR, and primary winding 6 of track transformer B'IT through common connection CC to the other terminal of the primary winding of transformer LT'I. Relay 9TB. at the opposite end N of the section is tuned by condenser I2 to be responsive to this cycle current and relay 9TB is caused to operate at the code rate to energize its associated relays SD, SE and QHP. Signal 9S accordingly is caused to display its normal clear aspect, and section N-O is supplied at N with current of the second (200 cycle) frequency over a circuit extending from one terminal of winding I5 of frequency changer FC through back contact 32 of relay IiSP, contact I80 of coder 3C1, front contact 4 operated by signal 9S and primary winding 6 of track transformer IOTT through common connection CC to the other terminal of winding I5. Relay I ITR at the opposite end 0 of section N-O is tuned by condenser I3 to be responsive to current of the second frequency available in the associated section, and relay I lTR accordingly operates at the 180 code rate to cause its associated relays HH and HP to be energized. Section OP is sup lied at O with current of the first (100 cycle) frequency over a circuit extending from one terminal of the secondary winding of line transformer LTH through back contact 34 of relay IZSP, back contact 33 of relay IZSR, front contact 30 when closed of relay l ITR, and primary winding 6 of track transformer IZTT through common connection CC to the other terminal of the secondary winding of line transformer LT! l It is to be noted that if relay |2SR operates its contact 33 from its back to its front position, and the other parts of the circuit just traced remain unchanged, then the energy supplied to track transformer IETT is carried through contact 20 of coder 401. This coder is provided with an energizing circuit extending from terminal B through back contact 35 of relay I2SP, front contact 35 of relay IZSR and' the winding of coder 4CT to the other terminal C of the source, and coder ACT when energized operates its contact 29 at a rate of 20 times per minute to thereby code at this rate energy supplied over the previously mentioned circuit including its own contact 2%. It follows therefore that under the above assumed conditions, the energy supplied thrcugh track transformer IZ'IT to the rails of section OP is coded at the 20 code rate.

Relay I3TR at the opposite end P of section OP is condition by condenser l2 to operate in response to current of the first frequency and relay I3TR operates at the 180 code rate due to the A 180 code current normally available in section OP. Relays l3H, l3I-IP, 13D, BSA and FSA associated with relay I3TR accordingly are energized, and signal I3S is caused to display its clear aspect.

The section extending to the right or to the east -of section OP is supplied at P with current of the, second frequency coded at the 180 code rate, over a circuit corresponding to that previously traced whereby the rails of section JK are supplied at J with track circuit current. Relay MTR at end P of the section to the right of section OP is normally conditioned to respond to current of the train control or 100 cycle frequency, and such relay normally operates at the 180 code rate in response to the 100 cycle current normally supplied to the section in a manner not shown but substantially corresponding to that hereinafter described in detail in connection with the supply of track circuit energy at K to section JK. Relays MH and MD associated with relay I ATR are energized, signal MS is caused to display its clear aspect, and overlap relay ISTP is energized in its normal direction over a circuit not shown but substantially corresponding to the circuit hereinafter traced for relay 3TP.

Section OP is supplied at P with current of the second frequency coded at the 180 code rate, over a circuit extending from one terminal of secondary winding l5 of frequency changer FC through back contact 44 of relay I3SR, contact I 80a of coder ECT, contact t (in its front position) operated by signal MS, primary winding 6 of track transformer I3TT and common connection CC to the other terminal of winding l5. Relay IZTR at the opposite end 0 of section OP is normally tuned by con-denser l3 to be responsive to 200 cycle current, and operation of relay I2TR at the 180 code rate causes its associated decoding relays 121-1 and IZHP to be picked up, and also causes current of the first frequency to be supplied to section N-O at 0 over a circuit extending from one terminal of the secondary winding of line transformer LTI I through back contact 38 of relay HSR, front contact 30 when closed of relay I2TR, and primary winding 6 of track transformer HTT through common connection CC to the other terminal of the secondary winding of transformer LTI I. Relay IBTR at the opposite end N of section N-O is normally tuned by condenser 12 to be responsive to 100 cycle current, and relay IOTR accordingly is normally caused to operate at the 180 code rate to cause its associated relays IUH and IUD to be picked up to control the associated signal MS to display its normal clear aspect.

Section MN is supplied at N with current of the second frequency over a circuit extending from one terminal of winding [5 of frequency changer FC through back contact 39 of relay 98R, contact |a of coder 3CT, front contact 4 operated by signal MS, and primary winding 6 of track transformer 9TT through common connection CC to the other terminal of winding [5.

Relay 8TR at the opposite end M of the section i is tuned by condenser l3 to be responsive to 200 cycle current, and relay 8TR accordingly operates at the 180 code rate to cause its associated relays 8H and 8I-IP to be energized. Overlap relay 8T? also is energized over an obvious circuit including front contact 57 of relay 8H.

Section L-M is normally supplied at M with 200 cycle current over a circuit extending from one terminal of winding [5 of frequency changer FC through back contact 40 of relay BSR, front contact 30 when closed of relay BTR, and primary winding 6 of track transformer 'ITT through common connection CC to the other terminal of winding l5. This current is caused to be coded at the 180 code rate in response to operation of relay 8TR by 180 code energy available in section M-N. Relay BTR at the opposite end L of the section is tuned by condenser I3 to be responsive to 200 cycle current, and relay BTR accordingly is caused to operate at the 180 code rate to cause its associated relays 6D, 6H and 6I-IP to be picked up to control the associated signal 68 to display its normal clear aspect. 7

Section K-L is supplied at L with 100 cycle current over a circuit extending from one terminal of the secondary winding of line transformer LT5 through back contact 4| of relay 5SR, contact I80a of coder ZCT, front contact 4 operated by signal 6S, and primary winding 6 of track transformer 5TT through common connection CC to the other terminal of the secondary Winding of transformer LT5. At the opposite end K of the section, relay 4TB is tuned by condenser [2 to be responsive to 100 cycle current, and relay 4TR accordingly is caused to operate normally at its code rate to cause its associated two relays 4H and 4HP to be picked up. Relay 4TB. has its contact 30 interposed in a circuit extending from one terminal of the secondary winding of line transformer LT3 through back contact 43 of relay 3SP, front contact 30 when closed of relay 4TB, and primary winding 6 of track transformer 3TT through common connection CC to the other terminal of transformer LT3, and current supplied over this circuit accordingly is normally coded at the 180 code rate, to cause relay ZTR at the opposite end J of the section to operate at the 180 code rate. Relay ZTR, as pointed out heretofore, normally is tuned by condenser 12 to be responsive to 100 cycle current, and relay ZTR operates in response to the 100 cycle current coded at the 180 code rate available in section J-K to cause its associated relays 2H and 2D to be picked up. Signal 28 is, therefore, normally caused to display its normal clear aspect.

The section extending to the left of section J-K is supplied at J with 200 cycle current over a circuit substantially Corresponding to the circuit hereinbefore traced and over which the rails of section OP are supplied at O with track circuit energy. This current is normally coded at the 180 code rate and is available to cause the track relay (not shown) connected at the opposite end of the section to operate at the 180 code rate. This track relay may, for example, be similar to relay IZTR heretofore mentioned as being provided at O for section OP.

From the foregoing description, it is apparent that the apparatus embodying my invention is arranged so that the two end sections J-K and MN of the single track stretch that extends between the two passing sidings Y and Z, are normally supplied with train control current (current having the frequency of 100 cycles per sec ond) which is transmitted through the rails toward the outer ends of such sections. Also, the track circuit apparatus provided for the siding sections is arranged so that 100 cycle current is transmitted through the rails toward the outer ends of such sections.

The apparatus embodying my invention is arranged in accordance with the A. P. B. principle of signaling, so that when a train enters the stretch extending between successive passing sidings, all signals governing opposing traffic movements up to the next passing siding in advance are caused to display their respective stop aspects, while the signals governing traffic in the direction of the train movement are controlled so as to permit following moves under permissive signal aspects governed by traffic conditions in advance. The apparatus further is arranged in such manner that when a train enters the single track stretch between passing sidings, in each of the track sections of the stretch the one track circuit associated with the direction of the train movement is supplied with current of the train control frequency, thereby rendering possible the control train-carried apparatus on the train.

I shall first describe the operation of the apparatus represented in the drawings for a westbound move. When a westbound train enters the first section (not shown) west of the first siding east of siding Z, relay MTR is caused to become inactive and overlap relay IETP is caused to reverse its polar contact members l4 and 21, in a manner substantially similar to that hereinafter described whereby relay 2TB- is caused to become inactive and overlap relay 3T? is caused to reverse its contact members I4 and 21 when the train enters section MN. Relay MTR is thus tuned to be responsive to current of the second (200 cycle) frequency, and current of the train control (100 cycle) frequency is supplied over reverse contact 21 of relay l5TP to the section extending to the right of section OP.

With relay MTR inactive, its associated relays MH and 14D release to cause signal MS to display its stop aspect, and to cause contact 4 operated thereby to operate from its front to its back position to shift the coding of current supplied at P to section OP from the 180 to the 75 code rate. Relay IZTR of section 0-? accordingly operates at the 75 code rate to repeat this code into section N-O, with the result that relay IOTR follows this '75 code energy to maintain relay llll-l .picked up but to release relay IUD. Signal 10S accordingly is caused to display its approach aspect. This condition of the apparatus is maintained until the train enters the section immediately to the east of section O--P, and when this happens, overlap relay |5TP is caused to release, in a manner substantially corresponding to that pointed out hereinafter whereby relay 3TP is caused to release when section JK is entered by the train. When relay I5TP releases, its contact 86 opens to open the circuit, including contact 4 (in its back position) operated by signal MS, over which circuit 75 code energy is supplied at P to section OP. Section O P is thus deprived of 200 cycle current normally supplied at P, and relay IZTR becomes inactive, thereby maintaining open its contact 30 and removing the 100 cycle current from section N-O with the result that relay IOTR. also becomes inactive to in turn cause a release of its associated relay IGH. Signal its accordingly is caused to display its stop aspect, and operates its contact member 4 from its front to its back position to shift the coding of the current supplied at N to section MN from the 180 to the 75 code rate. Relay 8TB at the opposite end M of section MN of course operates at the 75 code rate to code at this rate the energy supplied at M to section LM, and relay STR, at L also operates at the 75 code rate with the result that its associated relay 6D releases and its associated signal GS is caused to display its approach aspect.

The inactivity of relay IZTR of the section to the left of section N-O, causes its associated relays IZH and IZHP to release. Relay IISR is now energized over a pick-up circuit which may be traced from terminal B through back contact 25 of relay 12H, front contact 5| of relay IIHP, the winding of relay IISR, and back contact of relay IZSR to the other terminal C. Relay I ISR picks up to close its front contact 52 to prepare a stick circuit, and operates its contact 53 from its back to its front position t shift the tuning of relay HTR from 200 to cycle current. Contact 54 of relay IISR also closes to energize overlap relay HSP, which relay picks up to operate its contact 55 from its back to its front position to shift the tuning of relay IUTR from 100 cycle to 200 cycle current, and also operates its Contact 32 from its back to its front position to shift the frequency of current supplied at N to section NO from 200 cycles to 100 cycles. At this time, therefore, section N-O is supplied at N with 100 cycle current coded at the code rate, relay TB is tuned to respond to 100 cycle current and follows the 180 code energy available in section N--O to code at this rate the 100 cycle energy supplied at O to section OP, and relay IUTR is tuned to respond to 200 cycle current but is inactive due to the fact that relay IZTR is inactive and holds its front contact 3!] open to constantly interrupt the circuit over which current normally is supplied at O to section N-O. It follows, therefore, that in the siding sections, that is, sections NO and OP, current of a train control frequency is supplied in the direction toward a westbound train and hence is available to operate train-carried apparatus on such train.

When the westbound train enters section OP, relay I3'I'R is shunted, relays FSA, BSA, I3H, I SHP and 13D are released, and signal BS is caused to display'its stop aspect. Relay TB is shunted and relays IIH and HP associated therewith are released when the train enters section N-O, and relay SR is held energized over a stick circuit which extends from terminal B through back contact of relay HHP, front contact 52 and the winding of relay SR, and back contact 85 of relay I2SR to terminal 0.

As will be made clear hereinafter, the apparatus associated with the section to the right of section O-P is restored, when the train vacates the section, to its normal condition wherein overlap relay I5TP is caused to close its front contact 86 and operate its polar contacts [4 and 21 to their normal right-hand positions to tune relay MTR to respond to current of the train control (100 cycle) frequency and to cause current of the second (200 cycle) frequency to be supplied at P to the associated section.

When the train enters section MN, relay STR is shunted and its associated relays 9D, 9H and SHIP are released to cause the associated signal 98 to display its stop aspect. Relay 8TR at the opposite end M of the section also is shunted, its associated relays 8H and 81-11 are released, and overlap relay STP quickly releases to open its contact H33 interposed in a pick-up circuit, presently to be traced, of relay BSR, prior to that relay picking up at the end of its slow pick-up period. Relay 'ISR at location M is energized over a pick-up circuit extending from terminal B through back contact 25 of relay 8H, front contact 59 of relay IHP and the winding of relay FSR through back contact 60 of relay 88R to terminal C. Relay TSR accordingly picks up to close its front contact El and thereby prepares a stick circuit hereinafter mentioned.

With relay 8TB. of section MN shunted, its front contact 38 is held steadily open to deprive section L-M of energy normally applied thereto at M. Relay GTR at the opposite end of section LM thereupon becomes inactive, and its associated relays 6H and SHP release to cause signal 68 to display its stop aspect. Signal BS accordingly operates its contact 4 from its front to its back position, and with relay 68R released, the circuits previously mentioned over which section KL is supplied at L with track circuit energy are opened so that no track circuit energy is supplied to section KL at L. Relay 5SR at location L becomes energized over a pick-up circuit extending from terminal B through back contact 25 of relay 6H, front contact 63 of relay 5HP, the winding of relay 58R and back contact 64 of relay SSR to the other terminal of the source. Relay 5SR picks up to close its front contact 65 to complete a stick circuit path connected in multiple with contact 63 of relay 5I-IP.

W'hen signal ES at L operates its contact 4 from its front to its back position, as pointed out hereinbefore, to thereby deprive section KL of the track circuit energy normally supplied at L to such section, relay 4TR at the opposite end K of the section becomes inactive, relays 4H and 4HP associated therewith release, and relay 38R picks up over its pick-up circuit extending from terminal 13 through back contact 25 of replay its stop aspect and operate its contact 4 to its back position to shift the coding of current supplied at J to the section to the left of section J-K, from the 180 to the 75 code rate.

As mentioned previously, relays 58R and SSE at locations L and K, respectively, are energized. Relay 58R in picking up closes its front contacts 69 to shift the tuning of relay 5TB to current of the first frequency, while relay 3SR picks up to close its front contacts 14] and 28 to shift, respectively, the tuning of relay iTR to current of the second frequency, and the current supplied at K to section KL to the first frequency. Front contact #8 of relay 38R also closes to energize relay 3SP over an obvious circuit, and front contacts 15 and 11 of relay 38R close in addition to reverse the polarity of current supplied to overlay relap 3'IP. This latter relay is normally energized by current of what I shall term normal polarity supplied over a circuit extending from terminal B through back contact 76 of relay 38R, front contact of relay 31-1, the winding of relay 3TP and back contact H of relay 3BR to terminal C, and it is readily apparent from an inspection of the drawing that when front contacts 76 and ll of relay 3SR close, the polarity of current energizing relay 3TP is reversed. Relay 3T is therefore caused to shift its polar contacts i l and 2'! to their respective reverse positions to tune relay ZTR to respond to current of the second frequency, and cause the current supplied at J to section JK to be shifted to the first frequency.

The slow pick-up characteristics of relay BSP are selected so that relay 3SP picks up to close its front contact l8 at substantially the same instant that relay 3TP reverses its polar contacts M and 21. Front contact l8 of relay 3SP conditions condenser I2 to tune relay 3TR to respond to current of the first frequency. It follows, therefore, that whenrelays 58R, 38R and 3SP are energized and relay STP is energized by current of reverse polarity, the track circuit apparatus of sections J-K and KL are conditioned to supply current of the first or train control frequency toward a westbound train on the stretch, thereby rendering possible the control of train-carried apparatus on the train.

From the foregoing description, it is readily apparent that when a westbound train enters the single track stretch extending between the two passing sidings Y and Z, all of the opposing signals up to the next passing siding Y are caused to display their stop aspects to prevent opposing moves, and the track circuit energies supplied to the sections of the stretch are controlled in such manner as to supply current of the train control frequency to each of the sections in the direction toward an approaching westbcund train.

When the westbound train vacates section OP, relay I2TR is caused to operate in a manner to be made clear presently, and relays [2H and I2HP associated therewith are picked up. Relay HSR is now held energized over its stick circuit including back contact 5! of relay IIHP, and section NO is supplied at O with 200 cycle current coded at a rate corresponding to the rate of operation of relay IZTR, this energy being supplied over a circuit including winding l5 of frequency changer FC, front contact 38 of relay IISR, and contact 30 (when closed) of relay IZTR. As will be made clear presently, relay I2TR is caused to operate at this time at the 180 code rate, hence 180 code energy is supplied to section NO but is shunted by the train away from relay IUTR. When, however, the train vacates section NO, relay HlTR operates at the '180 code rate, being tuned at this time by condenser I3 to respond to 200 cycle current, and relays 19H and ED are picked up to cause signal HES to display its clear aspect. Contact i associated with signal its accordingly is operated from its back to its front position, and 180 code energy of the second frequency is supplied at N to section M--N, but this energy is at this time shunted by the train away from relay 8TB.

When the train enters section L-M, relay 'iTR is shunted, relays TH and iii? release, and relay JSR is stuck energized over a stick circuit including back contact 59 of relay THP, and front contact 6! and the winding of relay ESR. This stick circuit holds relay "15R picked up after the train vacates section M-N and relay 8TB operates, in response to the 180 code energy of the second frequency available in section M-N, to pick up the associated relays 8H and BHP. Relay 8TP also is caused to pick up to close its front contact 8% interposed in the previously mentioned circuit including contact of coder ECT, front contact 3'2 of relay USP, and contact t (in its back position) operated by signal 98, over which circuit 75 code energy of the frequency is applied at N to section NO. This energy causes relay ii TR to operate at the 75 code rate and pick up its associated relays HH and ill-1P, and release stick relay HSR. Front contact 54 of relay l lSR accordingly opens to deenergize relay HSP, whereupon contact 32 of relay HSP operates from its front to its back position to shift the frequency of energy applied at N to section NO from the train control (or first) frequency to the second frequency. Contact 55 of relay HSP also operates from its front to its back position to shift the tuning of relay IOTR from the second to the first frequency.

The release of relay HSR, at location 0, also causes operation of its contact 53 from its front to its back position to shift the tuning of relay 1 [TR from the first to the second frequency, and contact 38 of relay HSR operates from its front to its back position to shift the current supplied at O to section NO from the second to the first frequency. It follows, therefore, that when a Westbound train passes location M, the track circuit energies supplied to section N-O are restored to their normal condition, that is, the track circuit apparatus of section N-O is restored to the condition wherein relay iaiTR responds to current of the first frequency supplied at the opposite end of the section, and relay l iT'R. responds to current of the second frequency supplied to the section at end N. This current of the second frequency is coded at the 75 code rate and hence causes relay 1 ITR to operate and code at a corresponding rate the energy of the first frequency applied at O to section OP. Relay 13TH accordingly responds to this '75 code energy available in section OP and picks up relays FSA, BSA, 131-1 and HTTP, thereby causing signal N58 to display its approach aspect. It is to be noted that relay 138R is provided with slow pickup characteristics so selected that relay I3SR does not pick up even though relay BSA, at this time, picks up to close its front contact 34 while back contact 93 of relay I3HP, interposed in a circuit hereinafter traced for relay 133R, is closed.

When the train enters section K, L, relay B'I'R is shunted, relays 5D, 5H and 5H? associated therewith release so that signal 53 is caused to display its stop aspect, and back contact 63 of relay 5I-IP closes to complete the previously mentioned stick circuit for relay 553R, which circuit extends from terminal B through back contact 53 of relay 5HP, front contact 55 and the winding of relay 58R, and back contact 63 of relay ESE. to the other terminal C.

After the train vacates section L-M, relay 'iTR, responds to 75 code energy supplied at L to the section over a circuit including back contact 29 of relay ESE, contact of coder 2C1, front contact of relay 58R, and contact 4 (in its back position) operated by signal 53. Operation of relay lTR at this code rate is effective to repeat the 75 code energy into section M-N, and relay BTR operates to pick up relays 9H and SHP, thereby causing signal 98 to display its approach aspect, and causing operation of contact 4 of signal BS from its back to its front position to shift the coding of current supplied to section NO from the 75 to the code rate. This 130 code energy is repeated by relay iTR into section O-P to cause operation of relay l3TR at the code rate. Relay i3!) accordingly is picked up and signal I38 is caused to display its clear aspect.

In addition, when the train vacates section L M, relay BTR is caused to operate at the 180 code rate in response to energy of the second frequency repeated into section L--M at M due to the operation of relay BTR in response to 180 code energy available in section M-N. Relays 5H, HEP and 6D are therefore energized, and si nal BS is caused to display its clear aspect and operate its contact from its back to its front position, thereby completing an easily traced circuit over which energy of the second frequency coded at the 180 code rate is supplied at L to section KL. This energy is, of course, shunted away from relay STR while the train occupies section KL.

When the westbound train enters section J- K, relay 3TB is shunted and relays 3H and SHP associated therewith release. Back contact H of relay 3HP closes to complete a stick circuit for relay 38R, which circuit extends from terminal B through back contact H of relay 3I-IP, front contact l3 and the winding of relay 33R, and back contact 62 of relay @SR to terminal C. In addition, front contact 85 of relay 3H opens to open the previously traced circuit of relay 3TP, whereupon relay 3T? releases to open its front contact 88 interposed in the circuit previously traced and over which 75 code energy is supplied at J to the section to the left of section JK.

It is thus apparent that when the section at the exit end of the stretch is entered by the train, as for example, when section JK is entered by the westbound train, the section in advance for the direction of train movement is then deprived of track circuit energy. This deprivation of energy may be utilized to place at stop the opposing signal at the opposite end of siding Y, in a manner of course, available to cause operation of relay 4TB after the train vacates section K-L. When this happens, relays 4H and 4H? are picked up, but relay SSR is retained energized over its previously traced stick circuit. It is to be noted that each stick relay 38R and 48R at location K (and the corresponding stick relays at locations L, M, and also) is arranged to be energized over a back contact of the other stick relay, hence when one stick relay is energized it prevents energization of the other.

When the train enters the section extending to the left of section JK, relay ITR is shunted and the associated relays ID, IH, II-IP, FSA and BSA are released. Signal IS accordingly is caused to display its stop aspect, and operates its contact 4 from its front to its back position.

The previously mentioned operation of relay 4TB causes 180 code current of the second frequency to be repeated into section J-K over a circuit comprising winding l5 of frequency changer FC, front contact 43 of relay 3SP, contact 30 when closed of relay 4TB and winding 6 of transformer 3TT. This energy is of course shunted by the train away from relay 2TB at this time, but when the train vacates section JK, this energy causes operation of relay 2TB- at the 180 code rate and picks up relays 2H and 2D to cause signal 28 to display its clear aspect and operate its contact 4 to its front position. The previously traced circuit over which 180 code, 200 cycle current is supplied at J to the section to the left of section J-K is now completed, to condition the relay of such section to operate at the 180 code rate when the train vacates such section. Such relay is, therefore, conditioned to operate at the 180 code rate in a manner corresponding to that previously mentioned whereby relay IETR is caused to operate at the 180 code rate when the westbound train vacates section O-P.

At the time that the train vacates section JK, current of the first (100 cycle) frequency is supplied at J to section JK over a circuit previously traced and comprising contact 4 (in its back position) operated by signal is, contact 15 of coder ICT, and contact 21 of relay STP in its reverse position. This '75 code energy available in section JK operates relay 3TB, and is repeated by that relay into section KL where it causes operation of relay 5TB. At location K, relays 3H and 3H? are picked up and relay 3SR is released, while at location L, relays 5H and 5H? are picked up and relay ESR is released. The release of relay 38R shifts the tuning of shifts the frequency of current supplied at K to section KL from 100 to 200 cycles. Similarly, the release of relay 55R alters the tuning of relay 5TB from 100 to 200 cycle current, and changes the frequency of current supplied at L to section K-L from 200 to 100 cycles. In addition, the energization of relay 5H causes signal 55 to display its approach aspect and operate its associated contact A from its back to its front position to alter the coding of the current supplied at L to section TrM from the '75 to the 180 code rate. This 180 code energy is repeated by relay 'lTR. into section MN where it causes relay 9TB to pick up relay 9D and thus cause signal 9S to display its clear aspect.

Considering location K again, the release of relay SSR causes its front contact 13 to open and deenergize relay 3S1, and its back contacts 16 and H to close and energize relay 3TB with relay 4TB from 230 to 100 cycle current and energy of normal polarity. Relay 3TP thereupon closes its front contact 86, and shifts its polar contacts [4 and 21 from their reverse to their normal positions to shift, respectively, the tuning of relay ZTR to cycle current and the frequency of current supplied at J to section JK to 200 cycle current. Relay 3SP also releases to close its back contacts l3 and 43 at substantially the same instant that polar contacts l4 and 27 of relay STP assume their respective normal positions. Back contact [8 of relay 35? conditions relay 3TP to operate in response to 260 cycle current, and back contact iii of relay ESP shifts the frequency of current supplied at K to section J-K from 200 to 100 cycles.

From the foregoing, it is readily apparent that after the westbound train proceeds through sections J-K and K--L, the track circuit apparatus of these sections are restored to their normal condition, that is, relays ZTR and 4TB are tuned to respond to current of the first frequency supplied at the opposite ends of the sections, and relays 3TH and 5TB are tuned to respond to current of the second frequency supplied to their respective track circuits.

When relay ITR is caused to operate in response to 75 code energy made available in its associated section in the manner described in detail in connection with the corresponding section OP, the associated signal IS is caused to display its approach indication, and its associated circuit controlling contact 4 is operated from its back to its front position'to shift the code rate of energy supplied at J to section J-K from the '75 to the code rate. This causes relay 3TB. to operate at the 180 code to code at this rate the energy supplied at K to section K-L, and relay 5TB. associated with section K-L is caused to operate at the 180 code to energize its associated relay 5D, therebycausing the associated signal 5S to display its clear aspect.

Signal IS is caused to display its clear aspect, and the apparatus is restored to its normal condition, as represented in the drawings, when relay ITR, is caused to operate at the 180 code rate in response to energymade available in its associated section in a manner substantially corresponding to that described in detail hereinbefore in connection with the corresponding section O-P.

From the foregoing description, it is readily apparent that I have provided railway traffic controlling apparatus so arranged as to permit a westbound train to move over a single track stretch provided with signals controlled by the movement of the train in such manner as to prevent opposing eastbound moves while permitting following westbound moves under permissive signal aspects governed by traffic conditions in advance. In addition, it is apparent that the track circuit energies supplied to the sections of the stretch are so controlled that in each section, current of the train control frequency is supplied to the section in a direction so as to be transmitted toward the train, thereby rendering possible the control of train-carried apparatus on the train uniquely responsive to current of the train control frequency.

I shall now assume that with the apparatus represented in the drawings in its normal condition, an eastbound train enters the first section east of the first siding west of siding Y. When this happens, the track circuit energy normally available in the section to the left of section JK is shifted from the normal l80 code rate to the '75 code rate, in a manner substantially simi lar to that hereinafter explained whereby the code rate of the energy supplied to section O-? is shifted from the 180 code rate to the 75 code rate when the train enters section JK. Under the assumed conditions, relay ITR is caused to operate at the 75 code rate and relay ID associated therewith releases to cause the associated signal 'IS to display its approach aspect. This condition of the apparatus is maintained until the train occupies the section to the left of siding section Y, whereupon the code rate of energy available in the section to the left of section JK is shifted, in a manner to be made clear hereinafter, from the 75 to the 20 code rate, thereby causing operation of relay ITR at the 20 code rate, and releasing relays IE and II B. Signal IS at J accordingly is caused to display its stop aspect, contact 4 operated thereby assumes its back position to shift the coding of energy applied at J to section JK from the 180 to the 75 cod rate, relays .3TR and 5TB operate at the 75 code rate, and relay 5D releases to cause signal 58 to display its approach aspect.

At location J, relay ISR is picked up over a pick-up circuit extending from terminal B through back contact 93 of relay IHP, front contact 94 of relay BSA and the winding of relay ISR. to terminal C. Relay ISR. closes its front contact 95 to thereby prepare a stick circuit hereinafter traced, operates its contact member 96 from its back to its front position to shift the tuning of relay ITR from 100 cycle to 200 cycle current, and operates its contact member 44 from its back to its front position to shift the frequency of current supplied at J to the section to the right of section JK from 200 to 100 cycle current. This 100 cycle current is of course available when the train occupies the section to the left of section JK to cause operation of the train-carried apparatus When the train cupies this section, relay ITR is deenergized and inactive, and relays FSA and BSA associated therewith are released to complete the previously mentioned stick circuit of relay ISR, which circuit extends from terminal B through back contact 93 of relay. IHP, back contact 94 of relay ZBSA, front contact 95 and the winding of relay ISR to terminal C.

When the train enters section JK, relay ZTR is shunted and relays 2H and 2D associated therewith are released to cause signal 28 to display its stop aspect. In addition, relay 3TR is shunted and relays 3H, 3H? and 3TP associated therewith are released. Relay 48R now becomes energized over a pick-up circuit extending from terminal B through back contact 25 of relay 3H, front contact 98 of relay 4HP, the winding of relay 48R and back contact I8 of relay 3SR to terminal C.

With relay 9TB. inactive, its contact 39 is held continuously open to open the previously traced circuit over which 1200 cycle current normally is supplied at K to section KL. Relay 511?. at the opposite end L of the section accordingly becomes inactive, relays H and 5HP associated therewith release, signal 58 is caused to display its stop aspect, and relay GSR is picked up over a pick-up circuit extending from terminal B through back contact of relay 5H, front contact 99 of relay SHIP, the winding of relay SSH. and back contact I90 of relay SSR to terminal C.

When signal 58 at L operates to its stop position, its associated contact member 4 operates from its front to its back position. This opens the circuit previously traced over which section LM is supplied at L with track circuit energy, with the result that relay ITR becomes inactive and its associated relays II-I and 1H? release. Relay BSR now becomes energized over a pickup circuit extending from terminal B through back contact 25 of relay II-I, front contact IIiI of relay BHP, the winding of relay BSR and back contact I92 of relay "ISR to terminal C.

The inactivity of relay ITR causes its front contact 39 to remain open, thereby opening the previously traced circuit over which section MN is supplied at M with track circuit energy. Relay 9TR accordingly is caused to become inactive, and relays SD, SE and 9H? associated therewith are released to cause signal 98 to display its stop aspect. Relay 93R becomes energized, during the slow release interval of repeater relay QI-IP, over a pick-up circuit including back contact 25 of relay 9H, front contact 52 of relay 9H1, front contact I93 of relay STP and the Winding of relay 95R to terminal C.

With signal 98 at N caused to display its stop aspect, its associated contact member 4 is operated from its front to its back position to shift the coding of current supplied at N to section N-O from the normal 180 code rate to the 75 code rate. This 75 code energy is supplied at N to section NO over a circuit comprising winding I5 of frequency changer FC, back contact 32 of relay I I SP, contact I5 of coder 3CT, front contact 8| of overlap relay BTP, contact 4 in its back position, operated 'by signal 93, and winding 6 of transformer IIJTT, and this energy causes operation of relay I ITR at a corresponding rate to re peat this '75 code current into section O-P, as is readily apparent from an inspection of the drawings. The '75 code current in section O-P operates relay I3TR and releases relay I3D to cause the westbound signal I3S at the opposite end of siding Z to display its approach aspect, as pointed out heretofore.

As mentioned previously, relays 63R, 88R and 98B at locations L, M and N, respectively, are energized. The energization of relay 65R causes its contact member I94 to be operated from its back to its front position to shift the tuning of relay G'I'R from 200 to 100 cycle current, and also operates its contact member 29 from its back to its front position to shift the frequency of current supplied at L to section LM from 100 to 200 cycle current. The energization of relay 8SR causes its contact member I01 to b operated from its back to its front position to shift the tuning of relay ITR from 100 to 200 cycle current, and also to operate its contact member 40 from its back to its front position to shift the frequency of current supplied at M to section LM from 200 to 100 cycle current. In addition, relay 8SR operates its contact member I09 from its back to its front position to shift the tuning of relay BTR from '200 to 100 cycle current.

The energization of relay 93R is effective to operate its associated contact member I ID from its back to its front position to shift the tuning of relay STR from 100 to 200 cycle current, and also causes contact member 39 of relay 98R to operate from its back to its front position to shift the frequency of current supplied at N to section MN from 200 cycles to 100 cycles. It is readily apparent, therefore, that in sections LM and MN, the track circuit apparatus is controlled in response to the entrance of an eastbound train on section JK in such manner as to supply such sections with track circuit energy of train control frequency in such manner as to be transmitted through the rails of such sections toward an eastbound train.

When the train vacates the section to the left of section JK, relay ITR is caused to remain inactive, in a manner substantially corresponding to that hereinafter described in detail whereby relay |3TR remains inactive after the eastbound train vacates section OP. Signal IS accordingly continues to display its stop aspect and maintains its contact 4 in its back position to complete a circuit previously mentioned and comprising winding l of frequency changer FC, contact 21 of relay 3TP in its normal position, contact of coder ICT, back contact 4 operated by signal IS and winding 6 of transformer ZTT. Current of the second frequency coded at the 75 code rate is, therefore, supplied at J to section JK but is shunted by the train away from relay 3TR. At this time, however, the rails of the section to the left of section JK are not supplied at J with track circuit energy, since contact 4 operated by signal 2S is in its back position, and front contact 86 of relay 3TP is open.

Relay 4TR is shunted, and relays 4H and 4HP release, when the train enters section KL. Relay 4SR is now held energized over its stick circuit comprising back contact 98 of relay 4HP, front contact 91 and the winding of relay 4SR, and back contact 18 of relay 38R. After the train vacates section JK, relay 3TR operates in response to the 75 code energy available in the section, and repeats this energy into section KL where it is shunted by the train. Operation of relay 3TB is, however, efiective to cause relays 3H, 3HP and 3TP to pick up, whereupon front contact 86 of relay 3TP closes and 75 code energy of the first frequency is supplied at J to the section to the left of section JK. This energy functions to restore the track circuit apparatus of the associated section to its normal condition, in a manner substantially corresponding to that hereinafter described in detail whereby the track circuit apparatus of section OP is restored to its normal condition when 75 code energy of the first frequency is applied at P to section OP after the eastbound train has vacated the section to the right of section OP. At this time, however, it is deemed sufficient to state that after the '75 code energy is supplied to the section to the left of section JK, relay ITR is caused to operate at the 180 rate in response to energy of the second frequency, relays FSA, BSA, IH, IHP and ID are picked up, and signal IS is caused to dis- 5 play its clear aspect and operates its contact 4 to its front position, thereby shifting the energy supplied at J to section JK from the 75 to the 180 code rate and causing relay 3TB to repeat this 180 code into section KL. In addition, relay ISR at J releases when relay IHP opens its back contact 93, and relay ISR closes its back contact 56, to tune relay ITR to respond to current of the first frequency, and its back contact 44, to shift the current supplied at J to the rails of the section associated with relay I TR, from the first to the second frequency. As will be made clear presently, relay ITR continues to operate at the 180 code rate in response to energy of the first frequency made available in the section.

When the train enters section LM, relay BTR is shunted, its associated relays 6D, 6H and EH? release, signal 68 is caused to display its stop aspect and operates its contact 4 to its back position, and relay 68R is held energized over its stick circuit comprising back contact 99 of relay SI-IP, front contact H15 and the winding of relay BSR, and back contact lilfl of relay SSR. After section KL becomes vacated, relay 5TR operates at the code rate in response to energy repeated by relay 3TB into section KL, and relays 5H, BHP and 5D pick up to cause signal 58 to display its clear aspect and operate its contact 4 to its front position. The rails of section LM are, therefore, supplied at this time with current of the second frequency coded at the 180 code rate, but the train in the section shunts the energy away from relay lTR.

Section KL is also supplied at this time with '75 code energy of the first frequency, over a circuit comprising the secondary winding of line transformer LT5, back contact 4| of relay 5SR, contact 15a of coder ECT, front contact I06 of relay 68R, contact 4, in its back position, of signal 5S, and winding 6 of transformer ETT. Relay 4TR accordingly is caused to operate and repeat this 75 code energy into section JK to cause operation of relay 2TR at the 75 code rate. Relays 4H and 4HP associated with relay 4'I'R are picked up, while stick relay 4SR is released. At location J, relays 2H and 2D associated with relay ZTR are picked up, and signal 28 is caused to display its approach aspect and operates its contact 4 to its front position to shift the coding of current supp-lied at J to the section to the left of section JK from the '75 to the 180 code rate. I When the eastbound train enters section M-N, relay BTR is shunted and its associated relays 8H and 8HP release, relay BSR now being held energized over its stick circuit extending from terminal B through back contact [ill of relay 8HP, front contact Ill and the winding of relay 88R, and back contact I02 of relay 'ISR to terminal C. The release of relay 8H opens its front contact 51 to deenergize relay 8TP, with the result that front contact 8| of relay 8TP opens to open the previously traced circuit over which current of the second frequency coded at the 75 code rate is supplied at N to section N-O. Relay IITR accordingly becomes inactive, and re lays H H and IIHP associated therewith release. Relay 128R now becomes energized over a circuit extending from terminal B through back contact 25 of relay I I H, front contact 14 of relay IZHP, the winding of relay IZSR, and back contact 82 of relay Ii SR to terminal C. Relay iZSR picks up and closes its front contact H3 to energize relay IZSP, operates its contact 33 from its back to its front position, and closes front contact 36 to energize coder 4CT, Under the assumed conditions, current of the first frequency coded at the 20 code rate is supplied at O to section OP over a circuit extending from one terminal of the secondary winding of the line transformer LT l I through back contact 34 of relay IZSP, front contact 33 of relay IZSR, contact 20 of coder 4CT, and primary winding 6 of track transformer IZTT through common connection CC to the other terminal of the secondary winding of line transformer LT! I This 20 code current available in section OP causes operation of track relay I3TR at the opposite end at the 20 code rate, and thereby causes the associated relays ISH and |3HP to be released and signal |3S to display its approach aspect to provide the usual overlap protection. Stick relay IBSR now is energized over a circuit extending from terminal B through back contact 93 of relay I3I-IP, front contact 94 of relay BSA and the winding of relay I3SR to terminal 0. When relay ISSR picks up,

it'operates its back contact 96 to its front position to shift the tuning of relay |3TR from 100 to 200 cycle current, and also operates its contact member 4t from its back to its front position to shift the frequency of current supplied at P to section OP from 200 to 100 cycle current..

The slow acting characteristics of relay IZSP at O are selected so that relay IZSP picks up to operate its contact member H4 from its back to its front position to shift the tuning of relay IZTR from 200 to 100 cycle current, and to open its back contact 34 interposed in the circuit over which 290 cycle current is normally supplied to section OP, at substantially the same time that relay I3SR is caused to pick up. When back contact 34 of relay I2SP opens, relay |3TR becomes inactive, and relays FSA and BSA associated therewith release. Relay [38R is now held energized over an obvious stick circuit including back contact 93 of relay ISHP, back contact 94 of relay BSA and front contact 95 of relay I3SR. Relay IZTR of section OP, is however caused to operate at the 180 code rate in response to current of the first frequency supplied at P to section OP, and relay I ZTR functions to repeat this 180 code current into section NO to cause operation at a corresponding rate of relay IOTR. Relays NIH and IOD accordingly are energized and cause signal its to display its clear aspect.

After the train vacates section LM, relay .TR operates at the 180 code rate in response to the current supplied at L to section LM. Relays ?H and 'IHP are picked up, and relay ITR repeats the 180 code current into section MN, but this current is shunted by the train away from relay 9TR.

When the train enters section N-O, relay IUTR is shunted, its associated relays NH and MD are released, and signal IDS is caused to display its stop aspect. Contact 4 operated by signal 18S accordingly assumes its back position, and after the train vacates section MN, that section is supplied with current of the first frequency coded at the '75 code rate over a circuit including contact 4 operated by signal iO-S in its back position, contact of coder 3CT, and front contact 39 of relay 9SR. This 75 code energy causes relay BTR to operate at the '75 code rate, and relay 8TR functions to repeat this '75 code energy into section LM, thereby causing relay B'IR to operate at the '75 code rate to pick up its associated relays 6H and SHR Signal 68 is caused to display its approach aspect and operates its contact 4 to its front position to shift the coding of current supplied at L to section K-L from the 75 to the 180 code rate. Relay 4TR accordingly operates and repeats this energy into section JK, whereupon relay ZTR operates and picks up its associated relay 2D to cause signal 2S to display its clear aspect.

At this time, relay 9TB- is caused to operate at the 180 code rate in response to energy repeated by relay ITR into section MN, and relays 9H, 9H? and 9D are picked up to cause signal 98 to display its clear aspect and operate its contact 4 to its front position. Energy of the second frequency coded at the 180 code rate is supplied at N to section NO but is shunted by the train away from relay HTR.

The track circuit apparatus of sections LM and MN are also restored to their normal condition at this time, in response to the release of relays BSR, 8SR and 98R. Relay GSR releases when relay 61-1? at L picks up, and back contacts H14 and 29 of relay GSR close to shift, re-

spectively, the tuning of relay GTR to current of thesecond frequency, and'the frequency of current supplied at L to section LM to the first frequency. Relay R at M releases when relays 8H, 8HP and BTP associated with relay 8TB pick up in response to operation of relay BTR, and back contacts I01 and 40 of relay BSR close to shift, respectively, the tuning of relay 'ITR to current of the first frequency, and the frequency of current supplied at M to section L--M to the second frequency. Back contacts 109 and 3| of relay BSR also close so that relay 8TR is tuned to respond to current of the second frequency, and current of the first frequency is applied at M to section MN. Relay 9SR at N'releases when relay 9H picks up, and relay 98R closes its backcontacts I I9 and 39.. Back contact Ht of relay 98R shifts the tuning of relay 9'I'R to current of the first frequency, while back contact 39 of relay 98R conditions current of the second frequency to be supplied at N to section MN. It follows, therefore, that the releasing of relays BSR, BSR and 9SR, effected when the eastbound train vacates section MN, causes the track circuit apparatus of sections LM and MN to be restored to the normal condition wherein relays 'ITR and 9TR are conditioned to respond to current of the first or train control frequency, and relays 6TR and 8TR are 'conditioned to respond to current of the second frequency.

When the train enters section OP, relay I2TR is shunted, relays I2H and I2HP are released, and relay |2SR is provided with a stick circuit comprising back contact 14 of relay IZHZP, front contact 19 and the winding of relay I2SR, and back contact 82 of relay I ISR. This stick circuit holds relay IZSR energized after the train vacates section N-O and relay IITR operates at the code rate to pick up relays NH and IIHP. Although relay I ITR closes its front contact 30 at a rate corresponding to the code rate of energy in section N-O, track circuit energy isnot, at this time, applied at O to section OP since back contact 33 of relay IZSR is open. It follows, therefore, that when the train vacates section OP, relay I3TR remains inactive.

Relay MTR is shunted, relays [4H and MD are released, and signal MS is caused to display stop when the train enters the section extending to the right of section OP. Relay I5TP also is caused to release and opens its front contact 86, with the result that at this time no energy is applied at P to section OP. Energy coded at the 75 code rate is, however, applied at P to the section to the right of section OP, and relay ISTP accordingly is caused to pick up, when this section becomes vacated, in substantially the same manner that relay ST? is energized when the eastbound train vacates section J-K. Current of the first frequency, coded at the '75 code rate. is thereupon supplied at P to section OP over a circuit comprising the secondary winding of line transformer LTI3, front contact 44 of relay ISSR, contact 15a of coder 501, front contact 88 of relay I5TP, contact 4 in its back position, operated by signal MS, and primary winding 6 of transformer I3TT. Relay IZTR accordingly operates at the '75 code rate to pick up relays IZH and IZHP, and to repeat the '75 code energy into section NO where it causes operation of relay HlTR. Relay IOH thereupon picks up to cause signal HIS to display its approach aspect and operate its contact 4 to its front position to shift the coding of energy applied at N to section MN to the 180 code. This 180 code energy is repeated by relay BTR into section L-M to cause operation of relay BTR, whereupon relay 6D is picked up and signal 68 is caused to display its normal clear aspect.

The operation of relay IZTR, at the '75 code rate, as previously mentioned, also causes the track circuit apparatus of section OP to be restored to its normal condition effective to establish control over train-carried apparatus on a westbound train. This restoration is effected when relay IZSR. releases upon relay l2I-lP opening its back contact '14. Back contact 33 of relay I2SR accordingly closes, and during the slow release interval of relay IZSP, current of the second frequency is supplied to section OP at over a circuit comprising winding l of transformer LTI I, front contact 34 of relay I2SP, back contact 33 of relay IZSR, front contact 30 when closed of relay TR, and winding 6 of track transformer I2TT. This current is coded at the 180 code rate and relay ISTR accordingly operates and picks up the associated relays FSA, BSA, I3H, ISHP and |3D to cause the associated signal |3S to display its clear aspect and operate its contact 4 to its front position to shift the coding of current supplied at P to the section to the left of section OP, to the 180 code rate. In addition, relay i3SR is released when relay ISHP picks up, the relay I3SR closes its back contacts 96 and 44. Back contact 93 tunes relay ISTR to respond to current of the first frequency, while back contact 44 shifts the frequency of current supplied at P to section OP to the second frequency, The slow releasing characteristics of relay IZSP are selected so that relay IZSP releases at substantially the same instant that relay I3SR releases. When relay IZSP releases, back contact H4 closes to tune relay IETR to respond to current of the second frequency, and back contact 34 closes to shift the current supplied at O to section OP to the first frequency. It follows, therefore, that the apparatus of section OP is restored to its normal condition wherein relay IZTR responds to current of the second frequency supplied to the associated section at end P, and relay I3TR responds to current of the first frequency supplied to the section at the opposite end 0.

When signal its at P is caused to display its proceed or approach aspect to operate its contact member 4 from its back to its front position, the code rate of current supplied at P to section OP is shifted from the 75 to the 180 code rate to cause relay IZ'I'R to operate at such rate and repeat into section N--O this 180 code current, thus causing relay IOTR to operate at the 180 code rate to energize its associated relays Hill and IUD and cause the associated signal [US to display its clear aspect. The apparatus accordingly is restored to its normal condition as represented in the drawings.

, From the foregoing description, it is readily apparent that apparatus embodying my invention is arranged so as to permit an eastbound train to move through a single track stretch provided with signals so controlled by the movement of the train as to prevent opposing westbound moves While permitting following eastbound movements under permissive signal aspects governed by traffic conditions in advance. In addition, it is to be noted that such control of the signals is effected without the use of control line wires by providing each insulated section of the stretch of track with two track circuits, one of which is normally supplied with track circuit energy of the type effective to operate train-carried apparatus and the other of which is normally supplied with track circuit energy of the type ineffective to operate train-carried apparatus. These track circuits are so arranged that whenever a train enters the stretch and shunts the rails of the first section thereof, the track circuit energies supplied to the two circuits of each section are so controlled that in each of such sections the one track circuit associated with the direction of train movement is supplied with track circuit energy of the type adapted to control train-carried apparatus, thereby rendering effective train-carried traflic controlling apparatus on a train irrespective of the direction of movement of the train on the stretch.

Although I have herein shown and described only one form of railway trafiic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track including a track section, means for applying at opposite ends of said section differently characterized energies one of which has the characteristics effective for controlling train-carried apparatus, two track relays one at each end of said section, means for conditioning each of said relays to respond only to the characteristics of the energy applied at the opposite end of said section, means responsive to movement of a train on said stretch for depriving one end of said section of energy there normally applied, means eifective in the event that said section is deprived of said one energy to shift the energy applied at the opposite end from the other to the said one form of energy, and means also effective for causing said conditioning means to condition said relays to respond only to energy of the characteristics applied to the opposite end of the section.

2. In combination with a stretch of railway track including a track section, signals governing traffic in opposite directions in said section, a first track relay tuned to be responsive to alternating current of one frequency and a source of alternating current of another frequency connected across the rails at one end of said section, another track relay tuned to be responsive to current of said other frequency and a source of alternating current of said one frequency connected across the rails at the opposite end of said section, means for coding the current supplied to the rails from each of said sources in accordance with traific conditions in advance, means for controlling said signals by said two relays respectively in accordance with the rate at which current supplied to the relays is coded, means controlled by said track relays and effective when a train enters the stretch in a given direction for causing the removal of the current applied to the entrance end for the said given direction of movement, from all of the remaining sections, and means also controlled-by said track relays and effective when alternating current of said one frequency is removed from the entrance end of a section for shifting the frequency of current supplied to the exit end of that section from the said other to the said one frequency, said last mentioned means also being 

